Duplex motion picture projector



feb. 6, 1934. G. A. MITCHELL DUPLEX MOTION PICTURE PROJECTOR 4sheezs-sheei` 1 Filed July 2l, 1930 Invnor GeQryeJ. Mitchel@ Feb. 6,1934. G A, MVCHELL 1,945,863

DUPLEX MOTION- PICTURE PROJECTOR Filed July 21, 1930 4 Sheets-Sheet 2Feb. 6, 19?4., c a. A. MITCHELL 1,945,863

I DUPLEX MOTI-ON PICTURE PROJECTOR l Filed July 21 1930 4 sheets-sheet 5I an, 63 67C 87b Feb. 6? 1934., G. A. MITCHELL l DUPLEX MOTION PICTUREPROJECTOR 4 Sheets-Sheewtl 4 Filed July 2l, 1950 IIIL,

llllllllllllll. l 1| l Patentedv Feb. 6, 1934 PATENT OFFICE DUPLEXMOTION PICTURE PROJECTOR George A. Mitchell, Los Angeles, Calif.,assigner to Mitchell Camera Corporation, West 'Hollywood, Calif., acorporation of Delaware Application' July 21, 1930. sen-a1 No. 469,567

23 Claims.

invention relates generally to motion picture projectors, and it is ageneral object of the invention to provide a single projection machineadapted to carry two reels of lm and having transfer mechanism forchanging over from one lm to the other without substantiallyinterrupting the continuity of projection.

In large motion picture theatres it is common to achieve continuity ofprojection by providing a plurality of projectors, and when the filmreel' on one projector is finished that projector is stopped and anotherprojector having the next reel is simultaneously started. According tothis practice. however, at least two complete project- -ors` arerequired, which practice is not suited either to small motion picturetheatres or to the home. In all such situations in which the provisionof but a single projector is practicable, it is necessary whenever areel is to be changed to interrupt projection while the old film isremoved and the new one is threaded. The disadvantages of this practiceare self-evident.

I have accordingly provided a single machine having feed and take-upreels for each of two films, and having means for quickly changing fromthe projection of one film to the projection of the other, all withoutstopping to thread film, and without stopping the intermittent iilmmovement mechanism, and with but a slight interruption in projection. Inaccomplishing this purpose I havek provided, in my preferred embodiment,a machine having feed and take-up reels for two films, and withindividual driving sprockets for each film. The lmpasses down throughindividual film gates, each of which is movable to and from a commonprojection position. A single intermittent lm movement is provided atthe projection position for driving whichever of the two films is heldby its gate at that position. Means are then provided whereby the filmmoving sprockets and reels of the film which is at the projectionposition are connected to the projector drive, while the lm movingsprockets and reels of the other lm are disconnected. Accordingly, whileone reel of film is being projected another may be threaded on themachine, and when the first is nished the machine may be operated toremove that fllm from the projection position and to replace it with thesecond film, while simultaneously changing the drive from the first filmto the second, so that but a moments time is required for the transfer.

The details of how these ends are accomplished will be more fullyunderstood from the following detailed description of a presentpreferred embodiment of the invention, reference for this purpose beinghad to the accompanying drawings, in which:

Fig. l is a side elevation of a projector according to my invention;

Fig. 2is a longitudinal medial section of the projector, being insection taken as indicated by line 2 2 of Fig. 3;

Fig. 3 is a section taken as indicated by the broken line 3 3 of Fig. 2;05 Fig. 4 is a section as indicated by the broken line 4 4 of Fig. 2;

Fig. 5 is a front elevation of the projector;

Fig. 6 is a section taken as indicated by the une 6 6 of Fig. 2; 70

Fig. 7 is a fragmentary detail of the film arm and gate with the plateremoved; and

Fig. 8 is a vertical cross section of the film gate.

Certain parts of the projector usual and well known in the art, such asthe shutter, lamp house, projection lens, lm take-upprovlsions, etc.,are not herein referred to, as these may be of any well known form andmay be incorporated in a design with my projector in any suitablemanner.

In the drawings the numeral 10 indicates generally a hollow body framefor the projector, which frame may be supported by any suitablestandard, not shown. 'I'he forward portion of body 10 is formed with ahollow upwardly extending arm 11 for the mounting of the two feed reels12, and with a hollow downwardly extending arm 13 for the mounting ofthe two take-up reels 14.- Journaled at thel upper end of arm 11 in thetwo side walls l5 thereof are spindles 16 upon the outer ends of whichare removably mounted the feed reels 12, as clearly shown in Fig. 3. Theside walls 17 of the downwardly extending arm 13 similarly carrymounting spindles 18 for the take-up reels 14.

Mounted horizontally in the side walls 20 of the projector body at therear thereof is a horizontal transverse shaft 21, and rotatable andlongitudinally slidable thereon between walls 20 is a shiftabletransmission member 22. This transmission member 22 has a medial spurgear 23, which meshes with a driving gear 24 mounted on a shaft v24ajoumaled in the side walls of the frame.

Shaft 24a may be considered as the drive shaft of the projector, itbeing understood to be driven in any suitable manner, not shown. On thetwo sides. of gear 23 are internal clutch members 25 and 26, whilerotatably mounted on the two ends of shaft 21 within the side walls 20are the corresponding external clutch elements 27 and 28, respectively,the clutches 25, 27 and 26, 28 being adapted to be alternately closedand opened by shifting member 110 22 back and forth on shaft 21, in themanner to be hereinafter described in more detail. In the posi- `tion ofFig. 4 the clutch 25, 27 is closed, and the clutch 26, 28 is open, andit will be understood that by shifting the transmission member 22longitudi-l nally on shaft 21 the clutch 25, 27 will be opened and theclutch 26, 28 closed.

Around the peripheries of clutch elements 2t? and 28 are formed sprocketteeth to provide sprockets 30 for o pair of drive chains 31. These drivechains 31 pass from the top sides of sproolo ets 30 over sprockets 32mounted within the Side Walls 2li at the bese of the upwardly extendingarm 11, from there down through hollow poets to o. pair of sproolreto 35at the upper end of the dowriwerdltT extending oruzi it, end from therearound sprookete ET back up to the oprooii'eto 30 The upper sprockets 32are :rotatably on bearings ttl thief. 4l hy ho shaft t1, which theft ioSupported hetwee ete 32' lou o. eert t3. loriued with and :ineide i overwhioh l belt through t holt tu i i on the oorresoout nog re The lowereuri over "whiolfi peso down through ti" "eye ol hieruit' titi ot' the,oro i. oud eiuii' ifi' for oprooteto do flower the two reels 5t ou Fund li" ore t wedded iro smoel-reto fr ,l tliere u: e

relativoiy toot/s respectively, out pase over to the tot:

the outer endon o spootlwbly', the parte rototuhhr more o pinoeilitahiy' eimoorted in hrooire from the oppooite oi ii an :inoperativeoutside position (see ente Fig. 4) inwardly through on opening thesiowall 66 and the vertical post 3ft, to ou one projection positionedjeeeot woll tid v i A alined with, th ltght aperture (eee goto 4l. Forthe purpose of twin two erm E 6ft ore provided with spur 68 which, meshwith o, eiruglo horizonte' said rook 7i? heilig manually uotuetehlongitudinally in bearings ii io the oido we-ilo the projector andhaving imohs 'Z2 for ooo venienoe in operationn The o@ oo er-w rangedwith reference to 70 that when either of the gates is in the projectionposition adjacent Wall 66 the other is swung out to the inoperativeposition, and it will be understood that by shifting rack 70 to one.eide or the other,

ollf purpose the Wi t) 1 i 'to the other :n-d oloees opei l "ovided torthe edge o ooert'tu' The urojeotiou oo :lotuie center luie ot" o lomo(not showt l located to 'the i., iront oi? e urojeoti :o eperture :is Atforo jeotor ruouut 'Lens mount til is tot@ gitudinolly slidehle withino. mounting' tube el oortied between ti vertieoi posts dat et the frontof the orojeotor (see Fig. 5); ond is 01o-- eroiole therein for o:auruose .ond by moons here inofter to he eet o The lower end or theguide plate is provided, over the oertorations oi' the hlm passing therethrough, with :slots 42 through which poss the film moving" claw pins t3of the intermittent hlm movement, which is generally designated by thenumeral B4. Arly suitable intermittent hlm movement moy he used, the onehere shown for oimplioity embodying on oscillating claw erin olidinglyoivoted ut B6, ond actuated by o boxed com 37, which in 'turn is drivenby e drive shaft hu et the projection j f Drive shaft 87a is hereconventionally shown driven through a sprocket 87band chain 87e from asprocket 87d on the drive shaft 24a of the projector. Backing up thefilm on the side opposite the film movement is a spring pressed plate 88having slots 89 to pass the claw pins, this plate normally yieldinglyholding the film up to position, but permitting the claw pins to forcethe film outward until the perforations mesh therewith.

In changing over from one film to the other by operation of rack 70, theintermittent film movement 84 is not stopped, and it is for this reasonthe gates are mounted to move straight toward and away from the filmmoving claws during the engagement or disengagement of the films withthe claws. By this arrangement the film is simply brought straighttoward the claws, and the spring pressed backing-up plate 88 permits thefilm when first engaged by the pins to be forced back until the pinsmesh with the film perforations. And the arrangement is preferably suchthat in changing gates, the film initially at the projection position iscleared of the claw pins before its driving sprockets are unclutched.

When a short focal length lens is used the lens mount may be so close tothe filml gate that it will have to be moved each time the film ischanged to permit'the film gates to clear. Means are thereforepreferably provided for automatically moving the lens mount forward toallow the gates to pass as the film is changed, and then returning it tonormal position. For this purpose, there may be provided a lens mountoperating arm pivoted upon a bracket 101 extending from the projectorbody, the forward end of which has a slot 102 which takes a stud 103 setinto the top of the lens mount and extending upwardly through a slot 105in the supporting tube 81. The rear end of the arm is connected by meansof a link 107 with an arm 108 mounted on a gear which meshes with thegear 64 of gate 61, the arm 108 extending substantially at right anglesto link 107 when the link is in its extreme forward or normal position.In the embodiment here shown, gear 110 is one half the diameter of gear64, so that while the gear 64 rotates through 90 degrees in carrying thefilm Y gate 61 from the projection position to the inoperative position,the gear 110 rotates through 180 degrees, and therefore draws vthe link107 rearward and then moves it forward again to take the upper dottedline position shown in Figs. 3, 4 and 6. This movement of link 107operates arm 100 to move the lens mount forward and then rearward as thefilm gates are changed. When gate 60 is on'the projection axis and gate61 in the inoperative position, the arm 108 andv link 107 are in theupper dotted line position of the figures, but the arm 100 is again inposition to hold the lens mount in the rearward or projection position,as will be understood without further detailed description.

The complete operation of my projector will now be understood, but abrief summary will here be given. To project a reel of film, the reel isplaced on one of the feed reel spindles 16, and the film threaded overthe corresponding film sprockets and gate to the take-up reel, theproper loops 85 and 86 being provided, as previously described. The rack70, which may be considered as an operating member both for the swinginggates and for the clutches between the driving gear and the filmsprockets, is then operated to position the gate through which the filmhas been threaded, in projection position, and this operation alsoconnects the appropriate film driving sprockets and reels with thedriving gear. The projector drive may then be started, and the film willbe driven by the sprockets, reels and intermittent movement as in theusual manner.

During the projection of this reel, another reel of film may be placedon the other feed reel spindle 16 and threaded around the correspondingfilm sprockets, which are then stationary, passing through theinoperatively located gate and down to the take-up reel. When the firstreel 'is finished, the rack is actuated to remove it from the projectionposition and to replace it with the second film, and also to disconnectthe drive of the first film and connect the drive of the second, so thatprojection of the second film is started just as projection of the firstfilm is stopped. And during the change over from one film to the other,the projection lens is moved forwardly to allow the swinging gates topass, and then returned rearwardly to normal position.

It will be recognized that the illustrative system specificallydescribed herein is capable of considerable modification andrearrangement Without departing from the spirit and scope of myinvention; and it is therefore to be understood that the followingclaims embrace all such modifications and equivalent arrangements as mayfairly be construed to fall within the scope of my invention.

I claim:-

1. In a motion picture projector, the combination of a single filmengaging film movement, film guiding means for a first film adapted tomove said first film to and from a position of film engagement by saidfilm movement, and

film guiding means for a second film adapted to move said second film toand from a position of lm engagement by said film movement.

2. In a motion picture projector, the combination of a single filmengaging film movement, film guiding means for a first film adapted tomove said first film to and from a position of film engagement by saidfilm movement, film guiding means for a second film adapted to move saidsecond film to` andfrom a position of film engagement by said firstmovement, and a single operating means oppositely operable upon saidfilm guiding means whereby one film is moved to position for engagementby the film movement while the other film is removed from said position.

3. In amotion picture projector, the combination of a single filmengaging intermittent film movement, film guiding means for a first filmadapted to move said first film to and from a position of engagement bysaid intermittent film movement, film guiding means for a second filmadapted to move said second film to and from a position of engagement bysaid intermittent film movement, film moving means for continuouslylongitudinally moving said first film, film moving means forcontinuously longitudinally moving said second film, driving means forthe projector, and means for connecting said driving means with eitherof said film moving means.

4. In a motion picturel projector, the combinat-ion of a single filmengaging intermittent film movement, film guiding means for -a rst filmadapted to move said first film to and from a position of engagement bysaid intermittentl film movement, film guiding means for a second filmadapted to move said second film to and from a position of engagement bysaid intermittentnlm movement, nlm moving means for continuously-longitudinally moving said first nlm, nlm moving means for continuouslylongitudinally moving said second nlm, driving means for the projector,means for connecting said driving means with either of said film movingmeans, means adapted to operate oppositely said nlm guiding means,whereby one film is moved to position for engagement by the intermittentnlm movement while the other film is removed from said position, andmeans operatively associated with said last mentioned meansautomatically operable to cause connection of said projector drivingmeans with the means yfor continuously longitudinally moving the filmengaged at that time by the intermittent nlm movement.

5. In a motion picture projector, the combination of a frame, a singlenlm engaging intermittent film movement mounted on said frame, and apair of nlm gates movably mounted on said frame, each said gate adaptedfor carrying a nlm and each movable to and from a position in which thenlm is engaged by the intermittent nlm movement.

6. In a motion picture projector, the combination oi a frame, a singleintermittent film movement mounted on said frame, a pair of nlm gatesmounted on swinging arms pivoted on said frame, each said gate movableby swinging of its arm to carry a nlm to and from a position to beengaged by the intermittent nlm movement.

7. In a motion picture projector, the combination of a frame, a singleintermittent nlm movement mounted on said frame, a pair of nlm gates imounted on swinging arms pivoted on said frame,

each said gate having a guide way for a nlm, and each movable byswinging of its arm to carry its nlm to and from a position ofengagement by the intermittent movement.

8. In a motion picture projector, the combination of a frame, a singleintermittent nim movement mounted on said frame. a pair of nim gatesmounted on swinging arms pivoted on said frame, each said gate having aguide way for a nlm, and each movable by swinging of its arm to carryits nlm to and from a position of engagement by the intermittentmovement. a gear at tl1e\` pivot of each gate arm, and gear meansinter`` connecting said gears in such relation that operation oi.' thegears causes one gate arm to move its film toward the intermittentmovement and the other gate arm to remove its nlm from the intermittentmovement.

9. In a motion picture projector, the combination of a frame, a singleintermittent nlm movement mounted on said frame, a pairv of nlm gatesmounted on swinging arms pivoted on said frame, each said gate having aguide way for a nlm, and each movable by swinging of its arm to carryits nlm to and from a position of engagement by the intermittentmovement, a gear on each gate arm concentric with the pivot thereof, anda manually operable rack meshing with both said gears andlongitudinallyslidabie in the frame, the relation between said gearsbeing such that movement of the rack in one direction causes one gatearm to swing to move its nlm toward the intermittent movement and theother gate arm to swing to remove its nlm` from the intermittentmovement.

10. In a motion picture projector, the combination of a frame, a`singleintermittent nim movement mounted on said frame, a pair of nlm gatesmounted on swinging arms pivoted on said frame, each said gate having aguide way for a nlm, and each movable by swinging of its arm tu carryits film to and from a position of engagement by the intermittentmovement, means inlterconnecting said arms in such relation that as onegate arm moves to carry its film toward the intermittent movement theother gate arm moves to carry its nlm away from the intermittentmovement, means for each nlm for continuously longitudinally moving thatfilm, driving means for the projector, means for connecting said drivingmeans to either of said means Y gagement by the intermittent movement,vmeans interconnecting said arms in such relation that as one gate armmoves to carry itsnlm toward the intermittent movement the other gatearm moves to carry its film away from the intermittent movement, meansfor each :film for continuously longitudinally moving that nlm, drivingmeans for the projector, a pair of clutches one between said drivingmeans and each of said means for continuously longitudinally moving thefilm, and means controlled by the operation of the gate arms foroperating said clutches.

12. In a motion picture projector, the combination of a frame, a singleintermittent nlm movement mounted on said frame, a pair of film gatesmounted on swinging arms pivoted on said frame, each said gate having a.guide way for a nlm, and each movable by swinging of its arm to carryits nlm to and from a position of engage- 'ment by the intermittentmovement, a gear on each gate arm concentric with the pivot thereof, amanually operable rack meshing with both said.V gears and longitudinallyslidable in the frame, the relation between said gears being such thatmovement of the rack in one direction causes one gate arm to swing tomove its nlm toward the intermittent movement and the other gate arm toswing to remove its 'nlm from the intermittent movement, means for eachnlm for continuously longitudinally moving that nlm, driving means forthe projector, a pair of clutches one between said driving means andeach of said means for continuously longitudinally moving the film, andmeans controlled by the said rack for operating said clutches.

13. In a motion picture projector, the combination of a frame, a singleintermittent film movement mounted on said frame, a pair of film vgatesmounted on swinging arms pivoted on said frame, each said gate having aguide way for a nlm, and each gate arm movable on its pivot forwardly tocarry its nlm from a position of engagement by the intermittent movementto an inoperative position', means interconnecting said gate arms andoperable to move one gate toward the intermittent movement as it movesthe other away from the intermittent movement, said gates havingprojection apertures, a lens mount movably mounted in the frame andnormally located in front of the aperture of the gate positioned at theintermittent movement, and means actuated by virtue of exchanging gatesat the intermittent movement for removing the lens mount from its normalposition and then returning it, to allow the swinging gates to clearsaid lens mount during the exchange.

14. In a motion picture projector, the combination of a frame, a singleintermittent film movement mounted on said frame, a pair of film 'lgates mounted on swinging arms pivoted on said frame, each said gatehaving a guide way for a film, and each gate arm movable on its pivotforwardly to carry its film` from a position of engagement by theintermittent movement to an inoperative position, a gear on each gatearm concentric with the pivot thereof, gear means interconnecting saidgears and operable to move one gate arm toward the intermittent movementas the other gate arm is removed from the intermittent movement, saidgates having projection apertures, a lens mount longitudinally movablein the frame on the center line -of the projection aperture and locatedforwardly of said aperture, a gear meshing with one of the gate arminterconnecting gears, and means interconnecting said last mentionedgear and said lens mount and adapted to move the lens mount forwardlyfrom normal vposition and then return it during operation of the gearsto exchange gates at the intermittent movement. v

. 15. In a motion picture apparatus, the combination of an apertureplate before which a film is adapted to be moved, a lens mount mountedon the apparatus forwardly of said aperture plate and movable towardsand away from said aperture plate, a lm gate pivoted on the apparatus onan axis to one side of the aperture in the aperture plate so as to swingto a position adjacent the forward face of said aperture plate, and toswing from said position forwardly towards said lens mount, and a lensmount shifting linkage operatively associated with said plvoted gate andconnected to the lens mount, said linkage arranged to move the lensmount forwardly from the aperture plate during and by virtue of themovement of the gate forwardly from said aperture plate.

16. In combination, a motion picture apparatus having a single lightaperture, film engaging lm movement mechanism ladapted to move a filmpast the light aperture, and two film carrying gates mounted on -theapparatus and cooperatively shiftable thereonto move their respectivelms alternately into and out of cooperative engagement with said filmmovement mechanism.

17. In combination, a motion picture apparatus having a single lightaperture, and two Jm gates each pivoted on said apparatus to move intoand 'out of registration with said light' aperture, a lens mount mountedin said apparatus to move towards and away from said light aperture, andlens mount shifting means operated by the'shifting of said gates formoving the lens mount` away from and then back towards said lightaperture during exchanging of gates at the light aperture.

18. In combination, a motion picture apparatus having a single lightaperture, and two film gates each pivoted on said apparatus to move intoand out o! lregistration. with said light aperture, means operativelyinterconnecting said gates in such relation that one of the gates isremoved from registration with the aperture as the other gate is movedthereto, a lens mount mounted in said apparatus to move towards and awayfrom said light aperture, and lens mount shifting means operated by theshifting of said gates for moving the lens mount away from and then backtowards said light aperture during exchanging of gates at the lightaperture.

19. In combination, a motion picture apparatus havinga frame, means onsaid frame providing a single light aperture before which a film stripvmay be moved, two sets of film guide means on said frame for carryingvtwo lm strips, and a film guide-in each of said guide means setsrelativelyshiftable within its set to iiex and carry the intermediateportion only of a lm strip threaded on that set between positions in andout of optical alinement with said light aperture.

20. In combination, a motion picture apparatus having a frame, means onsaid frame providing a single light aperture before which a film stripmay be moved, two sets of nlm guide means on said frame for carrying twofilm strips in spaced paths along opposite sides of said light aperture,and a film guide in each of said guide means sets relatively shiftablewithin its set to iiex and carry the intermediate portion only of a lmstrip threaded on that set between positions in and out of opticalalinement with said light aperture.

21. In combination, a motion picture apparatus having a frame, means onsaid frame providing a single light 'aperture before which a film stripmay be moved, an intermittent ilm movement mechanism mounted on saidframe to engage and move a film past said light aperture, two sets ofguide means on said frame for carrying two lm strips, and a relativelymovable lm guide in each of said guide means sets for moving theintermediate -portion of a film strip threaded on that set between aposition in optical alinement with said light aperture and of engagementby said nlm movement mechanism, and a position out of optical alinementwith said aperture andfree of the film movement mechamsm.

22. In combination, a motion picture apparatus having a frame, means onsaid frame providing a single light aperture before which a nlm stripmay be moved, a pair of lm drive sprockets mounted on said frame abovesaid aperture and located on opposite sides thereof, a corref spondingpair of lm drive sprockets mounted on said frame below said aperture andon opposite sides thereof, said lower sprockets adapted to take filmstrips fed Adownwardly by said upper sprockets, a pair oi movable nlmguides on the frame taking the intermediate portions of the lm stripsbetween the upper and lower sprockets, said film guides movablerelatively to said4 23. In combinatioma motion picture apparatus havinga frame, means on said frame providing a single light aperture beforewhich a nlm strip may be moved, a. pair of iilm drive sprockets mountedon said frame above said aperture and located on opposite sides thereof,a corresponding pair of film drive sprockets mounted on said frame belowsaid aperture and on opposite sides thereof, a pair of film gatesadapted to take and guide vertically moving nlm strips, said gatesvertically pivoted on said frame on opposite sides of said aperture soas to horizontally carry lm strips passing therethrough from a positionof alinement with said aperture to positions on opposite sides thereof,al1 in such manner that lm strips fed downwardly from said upper'sprockets may be formed in loops to pass through said film gates andthen pass on to said lower

